Fuel economy of 7.4L (454) powered 3/4 ton suburban

[oil pan 4]

Yeah stock C/R is a Briggs and Stratton inspired 8:1 (rounded up).

I got the edelbrock 1405 carb on there with the smaller jetting appears to be really close to what it actually needs. I have not moved the wide band O2 over yet.
Set timing 4 degrees before tdc. It runs so much better.

[kir_kenix]

Glad to hear that you are moving in the right direction. Wide-band will really allow you to zero all the way into that perfect 'zone' for your set up, at your current elevation.

I'm really enjoying your progress, but I must admit I am ultimately much more excited about your diesel swap. I've followed your 6.2/6.5 Frankenstein, dual turbo adventure for a couple years now...and I'm excited about the new platform. You don't know how many time's I've looked at Suburban's on Craigslist itching to follow you down that path (except with a manual).

Good luck and have fun.

[oil pan 4]

The diesel and remade 700R4 will replace the 454/TH400 in this C2500 eventually.
The diesel will get its mild steel cross over pipe replaced with 2 inch 316alloy stainless and waste gate with side exit screamer pipe. It has to have a waste gate because when I go back down to sea level it will hit over 20psi and that's too much.
Then since the body on this C2500 I will install all the high voltage accessories I wanted to put on my old suburban but never did because I knew it would be a pita to move it all over.

[kir_kenix]

What other accessories can you go electric with? I know you are rocking an electric water pump, fuel pump, fans, air compressors, etc. Electric power steering would be awesome if you could get it to work reliably...it would really, really suck to have to park that tank with the gear ratios supplied with the stock gear box. If you get that far you might as well ditch the alternator and go completely beltless.

I just called a guy from Craigslist about a mint '89 Suburban (gasser unfortunately). I doubt he'll come down far enough for me to bite, but we will see how it goes. Incidentally, any tips besides crossing your fingers on identifying a good 6.2 block while it is installed? Besides looking to see if it's been aftermarket turbo'd, looking for one of those mythical "high nickel" early years, etc? Seems to be a lot of people dumping older diesels lately at ridiculously low prices...but I hate to grab a doner vehicle with a junk block.

[oil pan 4]

I may go back to a belt driven water pump.

How to find a good 6.2L block. Stay away from the 660 casting if you can. See the engine run if you can.
I have horrible luck with used engines so I just rebuild them.
The high Ni blocks are cool but don't get hung up on finding one.
I think the best 6.2 block are the ones machined during the years that GM made both 6.2 and 6.5 at the same factory. They fixed the 660 casting design flaw in this casting and the blocks were cast so they could be bored to 6.2 or 6.5L. When bored to 6.2 the cylinders are stupid thick. These blocks are as desirable if not more than the high Ni blocks.
Also go with small valve heads. The small valve heads rarely crack.

Problem with going beltless is the water pump, that's a constant 5 amp electrical draw. A belt driven coolant pump makes an alt delete much more possible.

Problem with some kind of on/off power steering is the hydroboost brake system. I say get a gasser (like I did) keep the vacuum brake booster and you can run on the highway with the P/S unhooked or on a clutch. I would like to come up with some kind of way to clutch the P/S.
Then replace the vacuum pump with an oil pump drive out of a military HMMWV.
The cam vacuum pump adds an additional 500 watt load at cruise RPM.
You can replace the always turning, almost always unneeded vacuum pump with an electric vacuum pump that can almost always stay off.

Also run a J-code intake manifold. I tested all three, C then J then F and went back to J.
I also installed a peninsular upper plenum, its made for an F code intake but with a little adaptor plate I made it fit.

If you are going to tow, get a 3/4 ton and stay with 2wd if you can stand it.
As far as I can tell there is minimal weight difference between 1/2 ton and 3/4 ton.
It looks like 4x4 half ton with a 350 will weigh more than a 2wd 3/4 ton with a 454.

I also noticed that the 454 suburbans are in pretty good condition. Have lower miles than SBC and diesel counterparts. For example the suburban I bought has 140k miles that's less than 5k per year average. Another one I looked at had just over 100k and there were a few survivor 3/4 ton 454 powered suburbans with under 50k.
All the 350s and diesels normally have way over 200k miles and people want way too much for them. For some reason 2wd 454 powered suburbans are not that desirable.

[kir_kenix]

"The cam vacuum pump adds an additional 500 watt load at cruise RPM.
You can replace the always turning, almost always unneeded vacuum pump with an electric vacuum pump that can almost always stay off."

I remember somebody running the pump and crunching the numbers a while back (may have even been you) and I'm still amazed by the 500 watt load.

I am going to have to go 4wd unfortunately...I just live too far in the sticks to even consider 2wd right now on this type of rig. Every time it rains or snows/thaws we need 4wd to make it out of my 3/4-1mile drive way/lane (huge hill for around here...no incentive for the county to drop gravel since I'm the only house on the lane).

However, I really only need to be able to pull 10-12,000 lbs with this rig. Anything more than that and I will bust out one of the trucks. So I could conceivable run 3.42's or higher instead of the 4.10's or 4.56's like a lot of guys are running.

I appreciate the information you have provided on 6.2's, and I'll keep it on mind while stalking craigslist. There are 3 trucks and 2 Suburban's within 100 miles of me that I plan on looking at this next week when I get home...crossing my fingers I can snag a good one.

[oil pan 4]

Yes I tested it.
3.42 are the most highway gear you are going to be able to find for full float 14 bolt.
I would love to find a 3.21 ring gear but no one makes them any more.
EDIT: NitroGear makes them.

[oil pan 4]

I may have located a source for GM 10.5'' full float 3.21 gears, at "thejeephut dot com".
(EDIT: the jeep hut does not have any 3.21 gears)
Says they are "discontinued" so I believe that means once they are gone, they are history, unless someone else does a production run.
Total for me looks like $307. I could easily save $300 in fuel swapping from the OE 4.10 gears to 3.42-3.21 in this pig.
The 3.21 gears and an ARB air locker and I will be all set.

Everywhere else I have looked might have the FF 10.5'' 14 bolt 3.21 gears listed but shows "not available" or has a price of "$0.00". Kind of makes sense that a jeep place would have them. I don't think GM full float 10.5 inch rears are popular with jeep guys. I think they like to stick with Dana or ford 9''.

The current half ton diesel setup is 31'' tires, 3.42 (10bolt) rear. The 3/4 ton suburban will have 32 inch tires and it looks like I will have the 3.21 gears now.
To counteract the taller gears and taller tires at low/start/stop speeds and keep from going from a tow monster to a towing turd I have a few alterations to make to the 6.5L/TH700R4 before it takes the place of the gasoline 7.4L/TH400.
1 More fuel. At the very least turn up my injector pump, maybe get one that can fire more fuel through the injectors.
2 Replace the torque converter, since the one on the TH700R4 is shot. The original OEMs diesel converter should be 900rpm stall. The one I found is 1200rpm built for diesels that go 4x4ing and/or tow.
3 Activate the VGT on the holset.
4 At higher speeds while towing revert the TH700R4 back to TH400 mode by putting it in 3rd gear.

In other news the rod and jet tuning kit came in, then a few hours later while I was at work another package with some additional smaller jets not included in that big kit arrived.

[oil pan 4]

I moved my AEM wideband O2 over into the suburban.
From my initial setting the idle was a tad too lean, needed about 1/8 of a turn rich to make it idle between the 16 to 18 range.

Gentile acceleration is lean, between 15 and 16 to one. That could burn a valve.
Moderate acceleration is around 15.
Flooring it meters fuel in at fuel at a rate of between 13 and 14 to one.
Cruise is around 16:1. I am pretty sure that is in the valve burn range.

I think I will start off by seeing what the next size smaller metering rod will do (will let in slightly more fuel during acceleration).

Edit: when I took the motor apart I pulled the exhaust valves and they showed no signs of burning.

[oil pan 4]

My Madmax tune looks like its going to be something like, 0.042'' accelerator pump jets (about 30% bigger than standard) running max stroke, 0.104'' secondaries (9% larger than standard and the largest standard metering jet), 0.95 primary jets (5% smaller than standard) with 7047 metering rods (standard).
I think the 0.95 primary jet will allow me to just replace metering rods to change normal driving charaistics.

The small accelerator pump nozzle was too small. Caused the engine to sputter. Tried the standard nozzle, also too small.

Now this carb is normally used on small block engines, ranging from 5L to about 6.6L.

I run the same carb in my Camaro and its jetting is totally different than this.
The primary, secondary and accelerator jets are all smaller.
The factory setup 1405 carb will run stupid rich all the time on a 5L at this elevation.

The same carb on a 454 will run kind of lean when you don't want it to, but then will run a little rich at cruse. Getting it to run a little lean at cruise is the trick and I think I got it.
I am sure its not going to be happy cold starting.

Edit: when I took the motor apart I pulled the exhaust valves and they showed no signs of burning.